*{
    padding: 0;
    margin: 0;
    text-decoration: none;
    list-style: none;
    box-sizing: border-box;
}
html,body,#app{
    height: 100%;
}
.container{
    height: calc(100% - 44px);
    background-color: gold;
    display:flex;
    flex-direction: column;
}
 .container>header{
    height: 44px;
    background-color: gainsboro;
 }
 .container>main{
    background-color: #fff;
    flex: 1;
    overflow-y: auto;
 }
  
footer{
    height: 44px;
    background-color: gainsboro;
}